Circular economy for plastic waste to polyethylene via refinery crude unit

ABSTRACT

Provided is a continuous process for converting waste plastic into a feedstock for polyethylene polymerization. The process comprises selecting waste plastics containing polyethylene and/or polypropylene, and then passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is then separated into offgas, a pyrolysis oil comprising a naphtha/diesel/heavy fraction, and char. The pyrolysis oil is passed to a crude unit in a refinery from which a naphtha fraction (C 5 -C 8 ), or a propane and butane (C 3 -C 4 ) fraction, is recovered. The naphtha fraction, or propane and butane (C 3 -C 4 ) fraction, is then passed to a steam cracker for ethylene production.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationNo. 62/952,636 filed Dec. 23, 2019, the complete disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

The world has seen extremely rapid growth of plastics production.According to PlasticsEurope Market Research Group, the world plasticsproduction was 335 million tons in 2016, 348 million tons in 2017 and359 million tons in 2018. According to McKinsey & Company, the globalplastics-waste volume was estimated about 260 million tons per year in2016, and projected to be 460 million tons per year by 2030 if thecurrent trajectory continues.

Single use plastic waste has become an increasingly importantenvironmental issue. At the moment, there appear to be few options forrecycling polyethylene and polypropylene waste plastics to value-addedchemical and fuel products. Currently, only a small amount ofpolyethylene and polypropylene is recycled via chemical recycling, whererecycled and cleaned polymer pellets are pyrolyzed in a pyrolysis unitto make fuels (naphtha, diesel), stream cracker feed or slack wax.

Processes are known which convert waste plastic into hydrocarbonlubricants. For example, U.S. Pat. No. 3,845,157 discloses cracking ofwaste or virgin polyolefins to form gaseous products such asethylene/olefin copolymers which are further processed to producesynthetic hydrocarbon lubricants. U.S. Pat. No. 4,642,401 discloses theproduction of liquid hydrocarbons by heating pulverized polyolefin wasteat temperatures of 150-500° C. and pressures of 20-300 bars. U.S. Pat.No. 5,849,964 discloses a process in which waste plastic materials aredepolymerized into a volatile phase and a liquid phase. The volatilephase is separated into a gaseous phase and a condensate. The liquidphase, the condensate and the gaseous phase are refined into liquid fuelcomponents using standard refining techniques. U.S. Pat. No. 6,143,940discloses a procedure for converting waste plastics into heavy waxcompositions. U.S. Pat. No. 6,150,577 discloses a process of convertingwaste plastics into lubricating oils. EP0620264 discloses a process forproducing lubricating oils from waste or virgin polyolefins by thermallycracking the waste in a fluidized bed to form a waxy product, optionallyusing a hydrotreatment, then catalytically isomerizing and fractionatingto recover a lubricating oil.

Other documents which relate to processes for converting waste plasticinto lubricating oils include U.S. Pat. Nos. 6,288,296; 6,774,272;6,822,126; 7,834,226; 8,088,961; 8,404,912 and 8,696,994; and U.S.Patent Application Publication Nos. 2019/0161683; 2016/0362609; and2016/0264885. The foregoing patent documents are incorporated herein byreference in their entirety.

The current method of chemical recycling via pyrolysis cannot make a bigimpact for the plastics industry. The current pyrolysis operationproduces poor quality fuel components (naphtha and diesel rangeproducts), but the quantity is small enough that these products can beblended into fuel supplies. However, this simple blending cannotcontinue if very large volumes of waste polyethylene and polypropyleneare to be recycled to address environmental issues. The products asproduced from a pyrolysis unit are of too poor quality to be blended inlarge amounts (for example 5-20 vol % blending) in transportation fuels.

In order to achieve recycling of single use plastics in an industriallysignificant quantity to reduce its environmental impact, more robustprocesses are needed. The improved processes should establish “circulareconomy” for the waste polyethylene and polypropylene plastics where thespent waste plastics are recycled effectively back as starting materialsfor polymers and high value byproducts.

SUMMARY

Provided is a continuous process for converting waste plastic intonaphtha for polyethylene polymerization. The process comprises firstselecting waste plastics containing polyethylene and/or polypropylene.These waste plastics are then passed through a pyrolysis reactor tothermally crack at least a portion of the polyolefin waste and produce apyrolyzed effluent. The pyrolyzed effluent is separated into offgas, apyrolysis oil and wax comprising a naphtha/diesel fraction and a heavyfraction, and char.

The incorporation of the process with an oil refinery is an importantaspect of the present process, and allows the creation of a circulareconomy with a single use waste plastic such as polyethylene. Thus, thepyrolysis oil and wax recovered is passed to a crude unit in a refinery.A naphtha fraction (C₅-C₈) is recovered from the distillation column,and the naphtha fraction is passed to a steam cracker for ethyleneproduction.

The refinery will generally have its own hydrocarbon feed flowingthrough the refinery units. The flow volume of pyrolysis oil and waxgenerated from the pyrolysis of waste plastic to the refinery units cancomprise any practical or accommodating volume % of the total flow tothe refinery units. Generally, the flow of the pyrolysis oil and waxgenerated from the waste plastic pyrolysis, for practical reasons, canbe up to about 50 vol. % of the total flow, i.e., the refinery flow andthe pyrolysis flow. In one embodiment, the flow of the pyrolysis oil andwax is an amount up to about 20 vol. % of the total flow.

In another embodiment, a continuous process for converting waste plasticcomprising polyethylene into a C₃-C₄ stream for polyethylenepolymerization is provided. The process comprises selecting wasteplastics containing polyethylene and polypropylene. The selected wasteplastics are passed through a pyrolysis reactor to thermally crack atleast portion of the polyolefin waste and produce a pyrolyzed effluent.The pyrolyzed effluent is separated into offgas, a pyrolyzed oil and waxcomprising a naphtha/diesel/heavy fraction, and char. The pyrolysis oiland/or optionally wax is passed to a crude unit distillation column in arefinery. A portion of a propane and butane (C₃-C₄) fraction isrecovered from the distillation column, and then passed to a steamcracker for ethylene production.

Among other factors, it has been found that by adding refineryoperations one can upgrade the waste pyrolysis oil and wax to highervalue products such as gasoline, and diesel. Also, by adding refineryoperations it has been found that clean naphtha (C₅-C₈) or C₃-C₄ can beefficiently and effectively produced from the waste pyrolysis oil andwax for ultimate polyethylene polymer production. Positive economics arerealized for the overall process from recycled plastics to apolyethylene product with product quality identical to that of virginpolymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the current practice of pyrolyzing waste plastics toproduce fuel or wax (base case).

FIG. 2 depicts a present process for establishing a circular economy forwaste plastics.

FIG. 3 depicts the plastic type classification for waste plasticsrecycling.

DETAILED DESCRIPTION

In the present process, provided is a method to recycle wastepolyethylene and/or polypropylene back to virgin polyethylene toestablish a circular economy by combining distinct industrial processes.A substantial portion of polyethylene and polypropylene polymers areused in single use plastics and get discarded after its use. The singleuse plastic waste has become an increasingly important environmentalissue. At the moment, there appear to be few options for recyclingpolyethylene and polypropylene waste plastics to value-added chemicalsand fuel products. Currently, only a small amount ofpolyethylene/polypropylene is recycled via chemical recycling, whererecycled and cleaned polymer pellets are pyrolyzed in a pyrolysis unitto make fuels (naphtha, diesel), steam cracker feed or slack wax.

Ethylene is the most produced petrochemical building block. Ethylene isproduced in hundreds of millions tons per year via steam cracking. Thesteam crackers use either gaseous feedstocks (ethane, propane and/orbutane) or liquid feed stocks (naphtha or gas oil). It is a noncatalyticcracking process that operates at very high temperatures, up to 850° C.

Polyethylene is used widely in various consumer and industrial products.Polyethylene is the most common plastic, over 100 million tons ofpolyethylene resins are produced annually. Its primary use is inpackaging (plastic bags, plastic films, geomembranes, containersincluding bottles, etc.). Polyethylene is produced in three main forms:high-density polyethylene (HDPE, ^(˜)0.940-0.965 g/cm⁻³), linearlow-density polyethylene (LLDPE, ^(˜)0.915-0.940 g/cm⁻³) and low-densitypolyethylene (LDPE, (<0.930 g/cm³), with the same chemical formula(C₂H₄)_(n) but different molecular structure. HDPE has a low degree ofbranching with short side chains while LDPE has a very high degree ofbranching with long side chains. LLDPE is a substantially linear polymerwith significant numbers of short branches, commonly made bycopolymerization of ethylene with short-chain alpha-olefins.

Low density polyethylene (LDPE) is produced via radical polymerizationat 150-300° C. and very high pressure of 1,000-3,000 atm. The processuses a small amount of oxygen and/or organic peroxide initiator toproduce polymer with about 4,000-40,000 carbon atoms per the averagepolymer molecule, and with many branches. High density polyethylene(HDPE) is manufactured at relatively low pressure (10-80 atm) and80-150° C. temperature in the presence of a catalyst. Ziegler-Nattaorganometallic catalysts (titanium(III) chloride with an aluminum alkyl)and Phillips-type catalysts (chromium(IV) oxide on silica) are typicallyused, and the manufacturing is done via a slurry process using a loopreactor or via a gas phase process with a fluidized bed reactor.Hydrogen is mixed with ethylene to control the chain length of thepolymer. Manufacturing conditions of linear low-density polyethylene(LLDPE) are similar to those of HDPE except copolymerization of ethylenewith short-chain alpha-olefins (1-butene or 1-hexene).

Today, only a small portion of spent polyethylene products is collectedfor recycling, due to the inefficiencies and ineffectiveness of therecycling efforts discussed above.

FIG. 1 shows a diagram of pyrolysis of waste plastics fuel or wax thatis generally operated in the industry today. As noted above, generally,polyethylene and polypropylene wastes are sorted together 1. The cleanedpolyethylene/polypropylene waste 2 is converted in a pyrolysis unit 3 tooffgas 4 and pyrolysis oil (liquid product), and at times wax. Theoffgas 4 from the pyrolysis unit is used as fuel to operate thepyrolysis unit 3. An on-site distillation unit (not shown) separates thepyrolysis oil to produce naphtha and diesel products 5 which are sold tofuel markets. The heavy pyrolysis oil fraction 6 is recycled back to thepyrolysis unit 3 to maximize the fuel yield. Char 7 is removed from thepyrolysis unit 3. The heavy fraction 6 is rich in long chain, linearhydrocarbons, and is very waxy (i.e., forms paraffinic wax upon coolingto ambient temperature). The wax can be separated from the heavyfraction 6 and sold to wax markets.

The present process converts pyrolyzed polyethylene and/or polypropylenewaste plastic in large quantities by integrating the waste polymerpyrolysis product streams into an oil refinery operation. The resultingprocesses produce the feedstocks for the polymers (naphtha or C₃-C₄ forethylene cracker), high quality gasoline and diesel fuel, and/or qualitybase oil.

Generally, the present process provides a circular economy forpolyethylene plants. Polyethylene is produced via polymerization of pureethylene. Clean ethylene can be made using a steam cracker. Eithernaphtha or a C₃-C₄ stream can be fed to the steam cracker. The ethyleneis then polymerized to create polyethylene.

By adding refinery operations to upgrade the waste pyrolysis oil and waxto higher value products (gasoline and diesel) and to produce clean LPGand naphtha for steam cracker for ultimate polyethylene polymerproduction, one is able to create positive economics for the overallprocess from recycled plastics to polyethylene product with qualityidentical to that of the virgin polymer.

A pyrolysis unit produces poor quality products containing contaminants,such as calcium, magnesium, chlorides, nitrogen, sulfur, dienes, andheavy components, which products cannot be used in large quantity forblending in transportation fuels. It has been discovered that by havingthese products go through the refinery units, the contaminants can becaptured in pre-treating units and their negative impacts diminished.The fuel components can be further upgraded with appropriate refineryunits with chemical conversion processes, with the final transportationfuels produced by the integrated process being of higher quality andmeeting the fuels quality requirements. The integrated process willgenerate a much cleaner naphtha stream for stream cracker feedstock forethylene generation and for polyethylene production. These large on-specproductions allow “cyclical economy” for the recycle plastics feasible.

The carbon in and out of the refinery operations are “transparent,”meaning that all the molecules from the waste plastic do not necessarilyend up in the exact olefin product cycled back to the polyolefin plants,but are nevertheless assumed as “credit” as the net “green” carbon inand out of the refinery is positive. With the integrated processes, theamount of virgin feeds needed for polyethylene plants will be reducedsubstantially.

FIG. 2 shows the present integrated process, integrating refineryoperations with recycle for effective polyethylene production. In FIG.2, mixed waste plastics are sorted together 21. The cleaned wasteplastic 22 is converted in a pyrolysis unit 23 to offgas 24 and apyrolysis oil (liquid product), and at times a wax (solid product atambient temperature). The offgas 24 from the pyrolysis unit can be usedas fuel to operate the pyrolysis unit 23. The pyrolysis oil isseparated, generally at an on-site distillation unit, into anaphtha/diesel fraction 25 and a heavy fraction 26. Char 27 is removedfrom the pyrolysis unit 23 after completion of the pyrolysis step.

The pyrolysis unit can be located near the waste plastics collectionsite, which site could be away from a refinery, near a refinery, orwithin a refinery. If the pyrolysis unit is located away from therefinery, then pyrolysis product (naphtha/diesel and heavies) can betransferred to the refinery by truck, barge, rail car or pipeline. It ispreferred, however, that the pyrolysis unit is within the plasticscollection site or the refinery.

The preferred starting material for the present process is sorted wasteplastics containing predominantly polyethylene and polypropylene(plastics recycle classification types 2, 4, and 5). The pre-sortedwaste plastics are washed and shredded or pelleted to feed to apyrolysis unit for thermal cracking. FIG. 3 depicts the plastic typeclassification for waste plastics recycling. Classification types 2, 4,and 5 are high density polyethylene, low density polyethylene andpolypropylene, respectively. Any combination of the polyethylene andpolypropylene waste plastics can be used. For the present process, atleast some polyethylene waste plastic is preferred.

Proper sorting of waste plastics is very important in order to minimizecontaminants such as N, Cl, and S. Plastics waste containingpolyethylene terephthalate (plastics recycle classification type 1),polyvinyl chloride (plastics recycle classification type 3) and otherpolymers (plastics recycle classification type 7) need to be sorted outto less than 5%, preferably less than 1% and most preferably less than0.1%. The present process can tolerate a moderate amount of polystyrene(plastics recycle classification type 6). Waste polystyrene needs to besorted out to less than 30%, preferably less than 20% and mostpreferably less than 5%.

Washing of waste plastics removes contaminants such as sodium, calcium,magnesium, aluminum, and non-metal contaminants coming from other wastesources. Non-metal contaminants include contaminants coming from thePeriodic Table Group IV, such as silica, contaminants from Group V, suchas phosphorus and nitrogen compounds, contaminants from Group VI, suchas sulfur compounds, and halide contaminants from Group VII, such asfluoride, chloride and iodide. The residual metals, non-metalcontaminants, and halides need to be removed to less than 50 ppm,preferentially less than 30 ppm and most preferentially to less than 5ppm.

If the washing does not remove the metals, non-metal contaminants, andhalide impurities adequately, then a separate guard bed can be used toremove the metals and non-metal contaminants.

The pyrolyzing is carried out by contacting a plastic material feedstockin a pyrolysis zone at pyrolysis conditions, where at least a portion ofthe feed(s) is cracked, thus forming a pyrolysis zone effluentcomprising olefins and n-paraffins. Pyrolysis conditions include atemperature of from about 400° C. to about 700° C., preferably fromabout 450° C. to about 650° C. Conventional pyrolysis technology teachesoperating conditions of above-atmospheric pressures. See e.g., U.S. Pat.No. 4,642,401. Additionally, it has been discovered that by adjustingthe pressure downward, the yield of a desired product can be controlled.See, e.g., U.S. Pat. No. 6,150,577. Accordingly, in some embodimentswhere such control is desired, the pyrolysis pressure issub-atmospheric.

FIG. 2 shows the present integrated process where the entire pyrolysisoil and wax from the pyrolysis unit is sent to a refinery crude unitdesalter 28. The crude unit desalter eliminates any contaminants in thepyrolysis product, then the product is sent to a crude unit distillationcolumn (not shown as part of the refinery crude unit). Alternatively,the pyrolysis oil and wax can be treated at the pyrolysis site to removethe contaminants, and then injected directly to the refinery crudedistillation unit.

The refinery crude unit separates crude oil into multiple fractions suchas liquefied petroleum gas (LPG), naphtha, kerosene, diesel and gas oilwhich will be further treated into useful petroleum products. Therefinery crude unit has a crude treating section, commonly known as adesalter, and a crude oil distillation or fractionation section. Thedistillation section typically includes an atmospheric distillation unitand a vacuum distillation unit.

The pyrolysis oil (and wax) is fed to the desalter which removes thesalts and solids contained in the oil to protect downstream equipmentfrom the harmful effects of the contaminants. To remove the salts, wateris mixed with the oil and typically heated to temperatures between about215° F. to about 280° F. and allowed to separate in the desalter unit.

The refinery will generally have its own hydrocarbon feed flowingthrough the refinery units. The flow volume of pyrolysis oil and waxgenerated from the pyrolysis of waste plastic to the refinery units cancomprise any practical or accommodating volume % of the total flow tothe refinery units. Generally, the flow of the pyrolysis oil and waxgenerated from the waste plastic pyrolysis, for practical reasons, canbe up to about 50 vol. % of the total flow, i.e., the refinery flow andthe pyrolysis flow. In one embodiment, the flow of the pyrolysis oil andwax is an amount up to about 20 vol. % of the total flow. In anotherembodiment, the flow of the pyrolysis oil and wax is an amount up toabout 10 vol. % of the total flow. About 20 vol. % has been found to bean amount that is quite practical in its impact on the refinery whilealso providing excellent results and being an amount that can beaccommodated. The amount of pyrolysis oil and wax generated from thepyrolysis can of course be controlled so that the fraction passed to therefinery units provide the desired volume % of the flow.

Desalted oil and wax is sent to an atmospheric distillation unit heatedto about 340-372° C. (644-700° F.) at the bottom of the distillationcolumn, and liquid is removed at various points of the fractionaldistillation column to produce various fuels. The fuels from the crudeunits can be sent to various upgrading units in the refinery to removeimpurities (nitrogen, sulfur) and to catalytically transform thefractions to improve the product properties, such as octane and cetanenumbers. The bottom residue from the atmospheric distillation column,also known as atmospheric residue, is typically sent to a vacuumdistillation column to produce vacuum gas oil (650-1050° F.) and vacuumresidue. The vacuum gas oil may be used to produce lube oil or furthercracked to produce gasoline, jet and diesel fuel. The overall processcan produce LPG (<80° F.), gasoline (80-400° F.), jet fuel (360-500°F.), and diesel fuel (300-700° F.). The boiling points for thesefractions are adjusted depending on the season and local specifications.

From the refinery crude distillation unit, a C₅-C₈ naphtha stream 29,preferentially a C₅-C₇ naphtha and most preferentially a C₅-C₆ naphthastream is collected. The light naphtha stream is rich in linearparaffins and is a very good light naphtha feed for a steam cracker 30to generate ethylene. The ethylene is passed on to a polymerization unit40 to produce polyethylene. The polyethylene is processed further toproduce various polyethylene products 41 to fit the needs of consumerproducts. The heavy portion of the pyrolysis oil can be combined withhydrocarbon from the crude unit distillation and sent to appropriaterefinery units as a heavy naphtha, diesel, atmospheric gas oil stream 31for upgrading into clean gasoline, diesel, or jet fuel.

The ethylene polymerization unit is preferably located near the refineryso that the feedstocks (propane, butane, naphtha) can be transferred viapipeline. For a petrochemical plant located away from the refinery, thefeedstock can be delivered via truck, barge, rail car or pipeline.

In another embodiment, a C₃-C₄ fraction 32 is recovered from therefinery crude unit 28. This stream can also be fed to the steam cracker30 for the production of ethylene. The ethylene is passed on to apolymerization unit 40 to produce polyethylene. The polyethylene isprocessed further to produce various polyethylene products 41 to fit theneeds of consumer products.

The benefits of a circular economy and an effective and efficientrecycling campaign are realized by the present integrated process.

The following examples are provided to further illustrate the presentprocess and its benefits. The examples are meant to be illustrative andnot limiting.

Example 1: Properties of Pyrolysis Oil and Wax From Commercial Sources

Pyrolysis oil and wax samples were obtained from commercial sources andtheir properties are summarized in Table 1. These pyrolysis samples wereprepared from waste plastics containing mostly polyethylene andpolypropylene via thermal decomposition in a pyrolysis reactor at around400-600° C., near atmospheric pressure without any added gas or acatalyst. A pyrolysis unit typically produces gas, liquid oil product,optionally wax product, and char. The pyrolysis unit's overhead gasstream containing thermally cracked hydrocarbon was cooled to collectcondensate as pyrolysis oil (liquid at ambient temperature) and/orpyrolysis wax (solid at ambient temperature). The pyrolysis oil is themain product of the pyrolysis units. Some units produce pyrolysis wax asa separate product in addition to the pyrolysis oil.

TABLE 1 Properties of As-Received Oil and Wax from Pyrolysis of WastePlastics Pyrolysis Oil Pyrolysis Oil Pyrolysis Oil Pyrolysis OilPyrolysis Wax Sample A Sample B Sample C Sample D Sample E SpecificGravity at 60° F. 0.814 0.820 0.774 — 0.828 Simulated Distillation, ° F.0.5% (Initial Boiling Point) 87 299 18 86 325 5% 179 306 129 154 475 10%214 309 156 210 545 30% 322 346 285 304 656 50% 421 447 392 421 733 70%545 585 517 532 798 90% 696 798 663 676 894 95% 772 883 735 743 93999.5% (Final Boiling Point) 942 1079 951 888 1064 Carlo-Elba HydrocarbonAnalysis Calbon, wt % 87.6 84.21 85.46 85.97 85.94 Hydrogen, wt % 12.712.25 14.1 14.0 14.15 Sum of C + H, wt % 100.3 96.46 99.5 100.0 100.1H/C Molar Ratio 1.73 1.75 1.98 1.96 1.98 Bromine Number, g/100 g 49 6040 44 14 Hydrocarbon Type Total Aromatics, vol % 23.3 22.8 5.1 8.7 13.3Total Olefins & Naphthenes, vol % 39.0 50.2 42.4 38.2 42.1 TotalParaffins, vol % 37.7 27 52.5 53.1 44.6 Contaminants Total S, ppm 48 297.8 99 6.3 Total N, ppm 751 1410 318 353 237 Total Cl, ppm 113 62 41 704.7 O in naphtha & distillate, ppm 250 — 574 — — Trace ElementalImpurities Al, ppm <1.1 <0.56 0.6 <0.53 <0.68 Ca, ppm 1.4 11.5 <0.5<0.53 <0.68 Fe, ppm 4.9 11.9 1.6 <1.1 3.1 Mg, ppm <0.51 1.3 <0.52 <0.53<0.68 Na, ppm 2.5 <0.54 <1.1 <2.2 <2.7 Ni, ppm <0.51 <0.54 <0.52 2 <0.68V, ppm <0.51 <0.54 <0.52 4 <0.68 P, ppm' 8.2 9.9 <1.6 <2.2 20.2 Si, ppm82.5 49.6 13 17 3.1

ASTM D4052 method was used for specific gravity measurements. Simulatedboiling point distribution curve was obtained using ASTM D2887 method.Carlo-Erba analysis for carbon and hydrogen was based on ASTM D5291method. Bromine number measurement was based on ASTM D1159 method.Hydrocarbon-type analysis was done using a high resolution magnetic massspectrometer using the magnet scanned from 40 to 500 Daltons. Totalsulfur was determined using XRF per ASTM D2622 method. The nitrogen wasdetermined using a modified ASTM D5762 method using chemiluminescencedetection. The total chloride content was measured using combustion ionchromatography instrument using modified ASTM 7359 method. The oxygencontent in naphtha and distillate boiling range was estimated using GCby GC/MS measurements with electron ionization detector for m/Z range of29-500. Trace metal and non-metal elements in oil were determined usinginductively coupled plasma-atomic emission spectrometry (ICP-AES).

Industrial pyrolysis process of sorted plastics, sourced predominantlyfrom polyethylene and polypropylene waste, produced quality hydrocarbonstreams with specific gravity ranging 0.7 to 0.9, and a boiling rangefrom 18 to 1100° F. as in pyrolysis oil or pyrolysis wax.

The pyrolysis product is rather pure hydrocarbon made of mostly carbonand hydrogen. The hydrogen to carbon molar ratio varies from 1.7 to near2.0. The Bromine Number is in the range of 14 through 60 indicatingvarying degrees of unsaturation coming from olefins and aromatics. Thearomatic content is in the range of 5 to 23 volume % with a higherseverity unit producing more aromatics. Depending on the processconditions of the pyrolysis unit, the pyrolysis products show paraffiniccontent ranging from mid-20 vol. % to mid-50 vol. %. The pyrolysisproduct contains a substantial amount of olefins. Samples A and B,pyrolysis oil produced under more severe conditions such as higherpyrolysis temperature and/or longer residence time, contain higheraromatic and lower paraffinic components, resulting H/C molar ratio ofaround 1.7 and high Bromine Number of 50-60. Samples C and D wereproduced at less severe conditions, and the pyrolysis oils are moreparaffinic, resulting H/C molar ratio of close to 2.0 and Bromine Numberaround 40. Sample E, pyrolysis wax, is mostly paraffinic, saturatedhydrocarbon with a substantial amount of normal hydrocarbons (as opposedto branched hydrocarbons) with low Bromine Number of only 14.

The following Examples 2 through 5 show the evaluation of waste plasticspyrolysis oil for transportation fuel.

Example 2: Fractionation of Pyrolysis Oil for Evaluation asTransportation Fuel

Sample D was distilled to produce hydrocarbon cuts representing gasoline(350° F.⁻), jet (350-572° F.), diesel (572-700° F.) and the heavy (700°F.⁺) fractions. Table 2 summarizes the boiling point distribution andimpurity distributions among the distilled product fractions.

TABLE 2 Distillation of Pyrolysis Oil into Fuel Fractions Sample IDSample D Sample F Sample G Sample H Sample I Intended Fraction GasolineCut Jet Cut Diesel Cut Unconverted Cut Point Target, ° F. 350⁻ 350-572572-700 700⁺ Distillation Actual Yields, wt % 37.2 38.0 15.0 9.3Simulated Distillation, F. IBP (0.5 wt %) 86 27 299 539 640 5 wt % 15498 345 557 684 10 wt % 210 147 365 574 696 30 wt % 304 222 416 597 72750 wt % 421 270 457 619 758 70 wt % 532 291 492 644 808 90 wt % 676 337546 674 898 95 wt % 743 347 554 683 953 FBP (99.5 wt %) 888 385 591 7111140 Total S, ppm 99 52 35 80 320 Total N, ppm 353 215 556 232 467 TotalCl, ppm 70 181 27 12 13

Example 3: Evaluation of Pyrolysis Oil Cut for Gasoline Fuel

Sample F, a pyrolysis oil cut for gasoline fuel boiling range, wasevaluated to assess its potential to use as gasoline fuel. Sample F hasthe carbon number range of C5-C12, typical of the gasoline fuel.

Due to the olefinic nature of the pyrolysis oil, oxidation stability(ASTM D525) and gum forming tendency (ASTM D381) were identified as themost critical properties to examine. Research octane number (RON) andmotor octane number (MON) are also the critical properties for engineperformance. The RON and MON values were estimated from detailedhydrocarbon GC analysis.

TABLE 3 Evaluation of Pyrolysis Oil Naphtha Fraction for Gasoline FuelOxidation Washed Stability, Gum, min mg/100 mL RON MON Sample F 90 5.071.4 67.7 Reference gasoline >1440 1 95.8 86.2 4/96 vol. % Blend ofSample F >1440 2.0 94.5 85.1 with reference gasoline 15/85 vol. % Blendof Sample F >1440 2.2 91.8 83.1 with reference gasoline

Sample F, a pyrolysis oil cut for gasoline fuel boiling range, cannot beused by itself as automotive gasoline fuel due to its poor quality. Thegasoline fraction from the pyrolysis oil showed very poor oxidationstability in that Sample F failed only after 90 min compared to thetarget stability of longer than 1440 minutes. The pyrolysis gasolineexceeded the wash gum target of 4 mg/100 mL suggesting severe gumforming tendency. The pyrolysis gasoline has poor octane numberscompared to the reference gasoline. A premium unleaded gasoline was usedas the reference gasoline.

We also examined the potential of blending of the pyrolysis gasoline cutfor a limited amount to the reference gasoline. Our study showed thatpossibly up to 15 volume % of Sample F can be blended to the refinerygasoline while still meeting the fuels property targets. By integratingthe pyrolysis gasoline product with a refinery fuel, the overall productquality can be maintained.

These results indicate that the as-produced gasoline fraction ofpyrolysis oil has limited utility as gasoline fuel. Upgrading in arefinery unit is preferred to convert this gasoline fraction of thepyrolysis oil into hydrocarbon that meets the gasoline fuel propertytargets.

Example 4: Evaluation of Pyrolysis Oil Cut for Jet Fuel

Sample G, a pyrolysis oil cut for jet fuel boiling range, was evaluatedto assess its potential to use as jet fuel. Sample G has the carbonnumber range of C9-C18, typical of the jet fuel.

Due to the olefinic nature of the pyrolysis oil, jet fuel thermaloxidation test (D3241) was considered as the most critical test. Thepyrolysis oil jet cut as-is, Sample G, had only 36 minutes of oxidationstability suggesting the pure pyrolysis jet cut is unsuitable for use asjet fuel.

We prepared a 5 volume % blend of pyrolysis jet cut (Sample G) withrefinery produced jet. The blend still failed for the jet fuel oxidationtest as shown in Table 4.

TABLE 4 Evaluation of Pyrolysis Oil Jet Fraction for Jet Fuel Jet FuelThermal Oxidation Test Reference jet fuel Passed 5/95 vol. % Blend ofSample G with reference jet fuel Failed

These results indicate that the as-produced jet fraction of pyrolysisoil is completely unsuitable for jet fuel, and upgrading in a refineryunit is required to convert this jet fraction of the pyrolysis oil intohydrocarbon that meets the jet fuel property targets.

Example 5: Evaluation of Pyrolysis Oil Cut for Diesel Fuel

Sample H, a pyrolysis oil cut for diesel fuel boiling range, wasevaluated to assess its potential to use as diesel fuel. Sample H hasthe carbon number range of C14-C24, typical of the diesel fuel.

Sample H contains a substantial amount of normal hydrocarbons. Sincenormal hydrocarbons tends to exhibit waxy characteristics, cold flowproperties such as pour point (ASTM D5950-14) and cloud points (ASTMD5773) were considered as the most critical tests.

We prepared two blends at 10 and 20 volume % of Sample H with refineryproduced diesel fuel. However, both blends still failed for the targetpour point of less than −17.8° C. (0° F.) pour points.

TABLE 5 Evaluation of Pyrolysis Oil Diesel Fraction for Diesel FuelCloud Point Pour Point Pour Point (° C.) (° C.) Test Reference dieselfuel −17.1 −19.0 Passed 10/90 vol. % Blend of Sample H −11.1 −12.0Failed with reference diesel fuel 20/80 vol. % Blend of Sample H −5.5−7.0 Failed with reference diesel fuel

These results indicate that the pyrolysis oil as-is is completelyunsuitable for diesel fuel, and upgrading in a refinery unit is requiredto covert the diesel fraction of pyrolysis oil into hydrocarbon thatmeets the diesel fuel property targets.

Examples 6: Coprocessing of Pyrolysis Product to Crude Unit or DesalterUnit

Results from Table 1 showed that industrial pyrolysis process of sortedplastics, sourced predominantly from polyethylene and polypropylenewaste, produced quality pyrolysis oil or pyrolysis wax made of mostlycarbon and hydrogen. With good sorting and efficient pyrolysis unitoperation, the nitrogen and sulfur impurities are at low enough levelsthat a modern refinery can handle cofeeding of pyrolysis feedstocks totheir processing units with no detrimental impacts.

However, some pyrolysis oils or wax may still contain high amounts ofmetals (Ca, Fe, Mg) and other non-metals (P, Si, Cl, O) that couldnegatively affect the performance of conversion units in a refinery. Forpyrolysis products with high impurity levels are preferentially fed to adesalter unit before by the crude unit so that bulk of impurities areremoved effectively by the desalter.

By feeding the entire pyrolysis feedstock to a crude unit or to adesalter unit before the crude unit, the pyrolysis oil and wax will befractionated into multiple components and then converted in thesubsequent conversion units including paraffin isomerization unit, jethydrotreating unit, diesel hydrotreating unit, fluid catalytic crackingunit (FCC), alkylation unit, hydrocracking unit and/or coker unit tomake gasoline, jet and diesel fuel with satisfactory product properties.The conversion units (FCC or hydrocracking unit) will also convert theheavy cut (corresponding to Sample I) or wax (Sample E) into qualitytransportation fuels.

After the crude unit, the pyrolysis oil and wax will be convertedfurther in the subsequent conversion units. The following Examples 7 and8 demonstrate the conversion of waste plastics pyrolysis product intoquality transportation fuel in a refinery conversion unit, using a FCCunit as an example.

Example 7: Conversion of Pyrolysis Oil in FCC

To study the impact of coprocessing of waste plastics pyrolysis oil toFCC, series of laboratory tests were carried out with Samples A and C.Vacuum gas oil (VGO) is the typical feed for FCC. FCC performances of20% blend of pyrolysis oil with VGO and pure pyrolysis oil were comparedwith that of the pure VGO feed.

The FCC experiments were carried out on a Model C ACE (advanced crackingevaluation) unit fabricated by Kayser Technology Inc. using regeneratedequilibrium catalyst (Ecat) from a refinery. The reactor was a fixedfluidized reactor using N₂ as fluidization gas. Catalytic crackingexperiments were carried out at the atmospheric pressure and 900° F.reactor temperature. The cat/oil ratio was varied between 5 to 8 byvarying the amount of the catalyst. A gas product was collected andanalyzed using a refinery gas analyzer (RGA), equipped with GC with FIDdetector. In-situ regeneration of a spent catalyst was carried out inthe presence of air at 1300° F., and the regeneration flue gas waspassed through a LECO unit to determine the coke yield. A liquid productwas weighted and analyzed in a GC for simulated distillation (D2887) andC₅ ⁻ composition analysis. With a material balance, the yields of coke,dry gas components, LPG components, gasoline (C5-430° F.), light cycleoil (LCO, 430-650° F.) and heavy cycle oil (HCO, 650° F.) weredetermined. The results are summarized below in Table 6.

TABLE 6 Evaluation of Pyrolysis Oil Cofeeding to FCC 20/80 vol % blend,20/80 vol % blend, 100% 100% Feed 100% VGO Sample A/VGO Sample C/VGOSample A Sample C Cat/Oil, wt/wt 6.0 6.0 6.0 6.0 6.0 Conversion, wt %*81.3 83.15 83.09 76.1 78.82 WLP Impurity** Total O, ppm 81 76 62 54 67Total N, ppm 27 30 33 50 21 Yields Coke, wt % 4.45 4.35 4.20 3.56 2.90Total Dry Gas, wt % 2.08 1.96 1.93 1.55 1.43 Hydrogen 0.16 0.12 0.120.05 0.04 Methane 0.68 0.65 0.64 0.50 0.46 Ethane 0.44 0.43 0.41 0.330.28 Ethylene 0.76 0.74 0.72 0.63 0.61 Total LPG, wt % 21.25 21.08 21.5020.17 24.40 Propane 1.78 1.76 1.72 1.47 1.53 Propylene 5.53 5.51 5.565.57 6.75 n-Butane 1.56 1.56 1.54 1.29 1.34 Isobutane 6.61 6.48 6.645.43 6.61 C4 olefins 5.77 5.77 6.04 6.41 8.16 Gasoline, wt % 53.53 55.7555.46 62.53 61.75 LCO, wt % 12.89 12.23 11.93 10.37 8.03 HCO, wt % 5.814.63 4.98 1.82 1.50 Octane Number*** 88.05 84.57 82.79 73.75 75.41*Conversion - conversion of 430° F.⁺ fraction to 430° F.⁻ **Impuritylevel of N and O in whole liquid product in fuels boiling range by GC ×GC, ppm ***Octane number, (R + M)/2, was estimated from detailedhydrocarbon GC of FCC gasoline.

The results in Table 6 show that up to 20 volume % cofeeding ofpyrolysis oil only makes very slight changes in the FCC unit performanceindicating coprocessing of pyrolysis oil up to 20% is readily feasible.The 20 volume % blending of Sample A or Sample C led to very slightreduction of coke and dry gas yields, slight increase in gasoline yieldand slight decrease in LCO and HCO, which are favorable in mostsituations. With paraffinic nature of pyrolysis oil, the 20% blends of Aand C lowered the Octane number by about 3-5 numbers. With refineryoperational flexibility, these octane number debits can be compensatedwith blending or feeding location adjustments. By cofeeding thepyrolysis oil through the FCC process unit with a zeolite catalyst, theoxygen and nitrogen impurities in the fuel range were reducedsubstantially, from about 300-1400 ppm N to about 30 ppm N and fromabout 250-540 ppm O to about 60-80 ppm O. The hydrocarbon composition ofall these cofeeding products are well within the typical FCC gasolinerange.

The FCC runs of 100% pyrolysis oil showed substantial debits of Octanenumbers by about 13-14 numbers. This shows that coprocessing ofpyrolysis oil is preferred over processing of pure 100% pyrolysis oil.

Example 8: Coprocessing of Pyrolysis Wax in FCC

To study the impact of coprocessing of waste plastics pyrolysis wax toFCC, series of laboratory tests were carried out with Sample E and VGO.FCC performances of 20% blend of pyrolysis wax with VGO and purepyrolysis wax were compared with that of the pure VGO feed, similar toExample 7. The results are summarized below in Table 7.

TABLE 7 Evaluation of Pyrolysis Wax Cofeeding to FCC 20/80 vol % blend,100% Feed 100% VGO Sample E/VGO Sample E Cat/Oil, wt/wt 6.5 6.5 6.5Conversion, wt %* 82.75 84.17 91.31 Yields Coke, wt % 4.78 4.76 4.26Total Dry Gas, wt % 2.11 2.05 1.79 Hydrogen 0.16 0.14 0.07 Methane 0.690.67 0.58 Ethane 0.44 0.43 0.37 Ethylene 0.78 0.77 0.73 Total LPG, wt %21.71 23.15 31.79 Propane 1.87 1.93 2.28 Propylene 5.54 5.98 8.59n-Butane 1.65 1.74 2.15 Isobutane 6.91 7.25 8.88 C4 olefins 5.74 6.259.89 Gasoline, wt % 54.16 54.21 53.47 LCO, wt % 12.42 11.59 6.71 HCO, wt% 4.83 4.24 1.99 Octane Number** 89.95 88.38 83.52 *Conversion -conversion of 430° F.⁺ fraction to 430° F.⁻ **Octane number, (R + M)/2,was estimated from detailed hydrocarbon GC of FCC gasoline.

The results in Table 7 shows that up to 20 volume % cofeeding ofpyrolysis wax only makes very slight changes in the FCC unit performanceindicating coprocessing of pyrolysis wax up to 20% is readily feasible.The 20 volume % blending of Sample E led to very slight reduction to nochange of coke and dry gas yields, noticeable increase in LPG olefinyield, very slight increase in gasoline yield and slight decrease in LCOand HCO, which are all favorable in most situations. With paraffinicnature of pyrolysis wax, the 20% blend of Sample E lowered the Octanenumber slightly by 1.5 number. With refinery blending flexibility, thisoctane number debit can be easily compensated with minor blendingadjustments.

The FCC run of 100% pyrolysis wax showed substantial increase inconversion, and debit of the Octane number by 6. This shows thatcoprocessing of pyrolysis wax is preferred over processing of 100%pyrolysis wax.

Example 9: Feedstocks of C₃-C₄ and/or Naphtha Generation from WastePlastics Pyrolysis Product Cofeeding to Refinery Crude Unit

By feeding of the entire pyrolysis feedstock to a crude unit or to adesalter unit before the crude unit, the pyrolysis oil and wax will befractionated into multiple components. With the pyrolysis oil cofeeding,the refinery crude unit produces a substantial amounts of clean propane,butane, and naphtha streams, as well as other streams for refineryconversion units.

Example 10: Feeding of Recycle C₃-C₄ and/or Naphtha to Steam Cracker forEthylene Production, Followed by Productions of Polyethylene Resin andPolyethylene Consumer Products

The propane, butane and naphtha streams, produced via cofeeding ofpyrolysis products to a crude unit per Example 9, are good feedstocks tocofeed to a steam cracker for production of ethylene with a recyclecontent. At least a portion of the streams, if not all, are fed to thesteam cracker. The ethylene is processed to a polymerization unit toproduce polyethylene resin containing somerecycled-polyethylene/polypropylene derived materials while the qualityof the newly produced polyethylene is indistinguishable to the virginpolyethylene made entirely from virgin petroleum resources. Thepolyethylene resin with the recycled material is then further processedto produce various polyethylene products to fit the needs of consumerproducts. These polyethylene consumer products now contains chemicallyrecycled, circular polymer while quality of the polyethylene consumerproducts are indistinguishable from those made entirely from virginpolyethylene polymer. These chemically recycled polymer products aredifferent from the mechanically recycled polymer products whosequalities are inferior to the polymer products made from virginpolymers.

As used in this disclosure the word “comprises” or “comprising” isintended as an open-ended transition meaning the inclusion of the namedelements, but not necessarily excluding other unnamed elements. Thephrase “consists essentially of” or “consisting essentially of” isintended to mean the exclusion of other elements of any essentialsignificance to the composition. The phrase “consisting of” or “consistsof” is intended as a transition meaning the exclusion of all but therecited elements with the exception of only minor traces of impurities.

All patents and publications referenced herein are hereby incorporatedby reference to the extent not inconsistent herewith. It will beunderstood that certain of the above-described structures, functions,and operations of the above-described embodiments are not necessary topractice the present invention and are included in the descriptionsimply for completeness of an exemplary embodiment or embodiments. Inaddition, it will be understood that specific structures, functions, andoperations set forth in the above-described referenced patents andpublications can be practiced in conjunction with the present invention,but they are not essential to its practice. It is therefore to beunderstood that the invention may be practiced otherwise that asspecifically described without actually departing from the spirit andscope of the present invention as defined by the appended claims.

What is claimed is:
 1. A continuous process for converting waste plasticinto naphtha for polyethylene polymerization comprising: (a) selectingwaste plastics containing polyethylene and/or polypropylene; (b) passingthe waste plastics from (a) through a pyrolysis reactor to thermallycrack at least a portion of the polyolefin waste and produce a pyrolyzedeffluent; (c) separating the pyrolyzed effluent into offgas, a pyrolysisoil and optionally pyrolysis wax comprising a naphtha/diesel fractionand a heavy fraction, and char; (d) passing the pyrolysis oil and wax toa crude unit in a refinery; (e) recovering a naphtha fraction (C₅-C₈)from the crude unit; (f) passing the naphtha fraction to a steam crackerfor ethylene production.
 2. The process of claim 1, wherein thepyrolysis oil and wax of (c) is passed directly to a refinery crude unitand the contaminants are removed in a crude unit desalter.
 3. Theprocess of claim 1, wherein contaminants are removed at the pyrolysissite.
 4. The process of claim 1, wherein the ethylene produced in (f) issubsequently polymerized.
 5. The process of claim 4, whereinpolyethylene products are prepared from the polymerized ethylene.
 6. Theprocess of claim 1, wherein heavy naphtha/diesel/atmospheric gas oil isrecovered from the crude unit and further processed in the refinery toclean gasoline, diesel or jet fuel.
 7. The process of claim 6, whereinthe amount of virgin crude oil processed by the crude unit is reducedwith recycled pyrolysis oil.
 8. The process of claim 1, wherein thewaste plastics selected in (a) are from plastics classification group 2,4 and/or
 5. 9. The process of claim 1, wherein the volume flow ofpyrolysis oil and wax to the crude unit in the refinery comprises up to50 volume % of the total hydrocarbon flow to the crude unit.
 10. Theprocess of claim 9, wherein the pyrolysis oil and wax flow comprises upto 20 volume %.
 11. A continuous process for converting waste plasticinto a C₃-C₄ stream for polyethylene polymerization comprising (a)selecting waste plastics containing polyethylene and/or polypropylene;(b) passing the waste plastics from (a) through a pyrolysis reactor tothermally crack at least portion of the polyolefin waste and produce andpyrolyzed effluent; (c) separating the pyrolyzed effluent into offgas, apyrolyzed oil and optionally wax comprising a naphtha/diesel fractionand heavy fraction, and char; (d) passing the pyrolysis oil to a crudeunit in a refinery; (e) recovering a portion of propane and butane(C₃-C₄) fraction from the crude unit; and (f) passing the C₃-C₄ fractionto a steam cracker for ethylene production.
 12. The process of claim 11,wherein the pyrolysis oil and wax of (c) is passed directly to arefinery crude unit and the contaminants are removed in a crude untildesalter.
 13. The process of claim 11, wherein contaminants are removedat the pyrolysis site.
 14. The process of claim 11, wherein the ethyleneproduced in (f) is subsequently polymerized.
 15. The process of claim11, wherein the polyethylene products are prepared from the polymerizedethylene.
 16. The process of claim 11, wherein heavynaphtha/diesel/atmospheric gas oil is recovered from the crude unit andfurther processed in the refinery to clean gasoline, diesel or jet fuel.17. The process of claim 11, wherein the volume flow of pyrolysis oiland wax to the crude unit in the refinery comprises up to 50 volume % ofthe total hydrocarbon flow to the crude unit.
 18. The process of claim17, wherein the pyrolysis oil and wax flow comprises up to 20 volume %.19. The process of claim 11, wherein the waste plastics selected in (a)are from plastics classification group 2, 4 and/or
 5. 20. A process forconverting waste plastic into chemicals useful in preparingpolyethylene, comprising: (a) selecting waste plastics containingpolyethylene and/or polypropylene; (b) pyrolyzing the waste plastic andrecovering a pyrolysis oil and wax comprising a naphtha/diesel/heavyfraction; and (c) passing the pyrolysis oil to a crude unit in arefinery.